No matter where you live, the first half of December provides some of the best meteor activity of the year. In the northern hemisphere the sporadic rates are still strong plus you can also count on strong activity from the Geminids, which peak on December 14. There are also several minor radiants that add a few meteors each hour. All of these centers of activity are located high in the sky during the early morning hours this time of year. Much of the activity mentioned above can also be seen from the southern hemisphere. While the sporadic rates are not as strong as those seen from the north, they are stronger than the previous months and heading for a maximum in January. The warm, but short summer nights south of the equator make for some great viewing as long as the moon does not interfere.
During this period the moon reaches its first quarter phase on Sunday December 12th. At this time the moon lies ninety degrees east of the sun and sets near midnight local standard time (LST) for those located in the mid-northern latitudes. Later next week the waxing gibbous moon remains above the horizon most of the night making meteor observing difficult. The estimated total hourly rates for evening observers this week is near eight from the northern hemisphere and two for observers south of the equator. For morning observers the estimated total hourly rates should be near forty-five from the northern hemisphere and twenty as seen from the southern hemisphere. The actual rates will also depend on factors such as personal light and motion perception, local weather conditions, alertness and experience in watching meteor activity. Evening rates are reduced this week due to moonlight.
The radiant (the area of the sky where meteors appear to shoot from) positions and rates listed below are exact for Saturday night/Sunday morning December 11/12. These positions do not change greatly day to day so the listed coordinates may be used during this entire period. Most star atlases (available at science stores and planetariums) will provide maps with grid lines of the celestial coordinates so that you may find out exactly where these positions are located in the sky. A planisphere or computer planetarium program is also useful in showing the sky at any time of night on any date of the year. Activity from each radiant is best seen when it is positioned highest in the sky, either due north or south along the meridian, depending on your latitude. It must be remembered that meteor activity is rarely seen at the radiant position. Rather they shoot outwards from the radiant so it is best to center your field of view so that the radiant lies at the edge and not the center. Viewing there will allow you to easily trace the path of each meteor back to the radiant (if it is a shower member) or in another direction if it is a sporadic. Meteor activity is not seen from radiants that are located below the horizon. The positions below are listed in a west to east manner in order of right ascension (celestial longitude). The positions listed first are located further west therefore are accessible earlier in the night while those listed further down the list rise later in the night.
The following showers are expected to be active this week:
Now that the activity from particles produced by comet 2P/Encke has ceased encountering the Earth, the Taurid showers for 2010 are over and we resume reporting activity from the Antihelion (ANT) radiant. This is not a true radiant but rather activity caused by the Earth's motion through space. As the Earth revolves around the sun it encounters particles orbiting in a prograde motion that are approaching their perihelion point. They all appear to be radiating from an area near the opposition point of the sun, hence the name Antihelion. These were once recorded as separate showers throughout the year but it is now suggested to bin them into their category separate from true showers and sporadics. This radiant is a very large oval some thirty degrees wide by fifteen degrees high. Activity from this radiant can appear from more than one constellation. The position listed here is for the center of the radiant which is currently located at 06:12 (093) +23. This position lies in western Gemini near the fourth magnitude star Eta Geminorum. Antihelion activity may also appear from eastern Taurus, northeastern Orion, or southern Auriga. This radiant is best placed near midnight LST when it lies on the meridian and is highest in the sky. Rates at this time should be near three per hour as seen from the northern hemisphere and two per hour from south of the equator. With an entry velocity of 30 km/sec., the average Antihelion meteor would be of slow velocity.
The Monocerotids (MON) are active from December 7th through the 18th. Peak activity occurred on December 8th. The radiant is currently located at 06:48 (102) +08. This position lies in northwestern Monoceros halfway between the bright stars Betelgeuse (Alpha Orionis) and Procyon (Alpha Canis Minoris). Current rates should be near one per hour no matter your location. The Monocerotids are best seen near 0100 LST when the radiant lies highest above the horizon. At 41 km/sec. the Monocerotids produce mostly meteors of medium velocity.
The Geminids (GEM) reach maximum activity on Monday evening/Tuesday morning December 13/14 when in excess of 60 shower members can be seen each hour from rural observing sites. The radiant is located at 07:28 (112) +32. This position lies in northern Gemini near the fourth magnitude star Rho Geminorum. This shower should be very activie this weekend with hourly rates near midnight ranging from 10 Friday night/Saturday morning to 25 Saturday night/Sunday morning. Although Geminid meteors can be seen all night long, they are best seen near 0200 LST when the radiant lies highest above the horizon. Geminid activity can be seen from the southern hemisphere but at much reduced rate. As seen from south of the equator, Geminid activity could only be seen for a few hours before and after 0200 LST. At 35 km/sec. the Geminids produce mostly meteors of medium velocity. This is one of the few displays that can be well seen prior to midnight. Unfortunately the first quarter moon will reduce rates until it approaches the western hornizon near midnight.
The Puppid-Velids (PUP) are a vast complex of weak radiants located in the constellations of Puppis and Vela. Visual plots and photographic studies have revealed many radiants in this area during November and December. The combined strength of these radiants can produce a ZHR of ten. Actual hourly rates will be much less unless you happen to be observing from the deep Southern Hemisphere. The center of this activity is currently located at 08:08 (126) -45. This position lies in western Vela, five degrees northeast of the second magnitude star Gamma Velorum. Peak rates occurred near December 7 so current activity is waning These meteors are best seen near 0300 LST when the radiant lies highest above the horizon in a dark sky. Observers located in the Southern Hemisphere have an advantage viewing this shower as the radiant will rise higher into their sky allowing more activity to be seen. At 40 km/sec. the Puppid-Velids produce meteors of average velocity.
The Sigma Hydrids (HYD) are active from November 26 through December 20. Maximum activity occurred on December 6. The radiant is currently located at 08:16 (129) +02. This position lies in western Hydra, just below the group of fourth magnitude stars that make up the "head" of the water serpent. These meteors are best seen near 0300 LST when the radiant lies highest above the horizon. Current rates would be near one per hour no matter your location. At 61 km/sec. the Sigma Hydrids produce mostly swift meteors.
The December Leonis Minorids (DLM) are active from a radiant located at 10:22 (155) +34. This position lies in central Leo Minor, approximately ten degrees north of the third magnitude star Zeta Leonis. These meteors are best seen near 0500 LST when the radiant lies highest above the horizon. This shower peaks on December 20th so current rates would be near one per hour as seen from the northern hemisphere and less than one per hour as seen from south of the equator. At 64 km/sec. the December Leonis Minorids produce mostly swift meteors.
Activity from the Coma Berenicids (COM) has just begun for 2010. The radiant is located at 11:30 (172) +19. This position actually lies in eastern Leo, six degrees northwest of the second magnitude star Denebola (Beta Leonis). These meteors are best seen near 0600 LST when the radiant lies highest above the horizon. This shower peaks on December 16th so current rates would be near two per hour as seen from the northern hemisphere and one per hour as seen from south of the equator. At 65 km/sec. the Coma Berenicids produce mostly swift meteors.
Another shower verified by video means are the Psi Ursa Majorids (PSU). This shower is active from November 29-December 13 with maximum activity occurring on December 5. The radiant is currently located at 11:55 (179) +41. This position lies in southern Ursa Major, one degree south of the third magnitude star Psi Ursae Majoris. This area of the sky is best placed during the last hour before dawn, when it lies highest above the horizon in a dark sky. With the shower ending this weekend, current rates would most likely be less than one per hour. At 61km/sec., the average Psi Ursa Majorid meteor would be swift.
Lastly, the December Alpha Draconids (DAD) are active from a radiant located at 14:00 (210) +58. This position actually lies in northeastern Ursa Major, six degrees northeast of the second magnitude double star Mizar (Zeta Ursae Majoris). These meteors are best seen during the last dark hour before dawn, when the radiant lies highest above the horizon in a dark sky. This shower is not well seen from the southern hemisphere. Expected hourly rates would be less than one no matter your location. At 44 km/sec. the Alpha Draconids produce mostly medium speed meteors.
As seen from the mid-northern hemisphere (45N) one would expect to see approximately twelve Sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near two per hour. As seen from the mid-southern hemisphere (45S), morning rates would be near eight per hour as seen from rural observing sites and one per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Evening rates are reduced by moonlight during this period.
The table below presents a condensed version of the expected activity this week. Rates and positions are exact for Saturday night/Sunday morning.
|SHOWER||DATE OF MAXIMUM ACTIVITY||CELESTIAL POSITION||ENTRY VELOCITY||CULMINATION||HOURLY RATE||CLASS*|
|RA (RA in Deg.) DEC||Km/Sec||Local Standard Time||North-South|
|Antihelion (ANT)||-||06:12 (093) +23||30||0100||3 - 2||II|
|Monocerotids (MON)||Dec 08||06:48 (102) +08||41||01:00||1 - 1||II|
|Geminids (GEM)||Dec 14||07:28 (112) +32||35||02:00||25 - 5||I|
|Puppid-Velids (PUP)||Dec 07||08:08 (126) -45||40||03:00||<1 - 2||II|
|Sigma Hydrids (HYD)||Dec 06||08:16 (129) +02||61||03:00||1 - 1||II|
|December Leonis Minorids (DLM)||Dec 20||10:22 (155) +34||71||05:00||1 - <1||II|
|Coma Berenicids (COM)||Dec 16||11:30 (172) +19||65||06:00||2 - <1||II|
|Psi Ursa Majorids (PSU)||Dec 05||11:55 (179) +41||61||06:00||<1 - <1||IV|
|December Alpha Draconids (DAD)||Dec 05||14:00 (210) +58||44||08:00||<1 - <1||IV|